APPLICANT'S ABSTRACT: The goal of this project is to examine the interaction of the extent of alcohol use and stage of HIV infection on prevalence, severity, and progression of cognitive function in HIV infection. Both HIV infection and alcohol use have been shown to influence brain function, but the specific contribution of alcohol use to cognitive dysfunction in the context of HIV infection has not been well studied. Alcohol use (or abuse) is very common among the largest risk group in the HIV epidemic (homosexual/bisexual men). However most studies of the effects of drugs in HIV infection have been with IV drug users, although this represents a small proportion of the overall HIV epidemic. There has been very little attention directed specifically at the effects of alcohol use in HIV infected individuals. Therefore it is important to investigate how alcohol use affects cognitive function in non drug using HIV infected people. This project will examine the independent and interactive effects of alcohol use and HIV infection on domains of cognitive function. Subjects will be recruited from numerous local community sources and the sample will be stratified on the basis of extent of alcohol use and stage of HIV infection. Stage of infection will be based on the current CDC criteria and extent of alcohol use will be based on syndromic diagnoses and quantitative estimates of alcohol use. Subjects will receive an extensive neuropsychological examination, structured psychiatric interviews, measures of Quality of Life and subjective symptom ratings. The data will be analyzed using factorial ANOVA or MANOVA as well as multiple regression analyses. The PI will also follow these subjects longitudinally to study the effects of patterns of alcohol use on changes in cognitive function and disease progression. It is hypothesized that in addition to significant effects for severity of alcohol use and stage of infection, there will also be a significant interaction with the effects of alcohol use being greater with increasing severity of HIV illness.